Electrochromic device having improved light stability

ABSTRACT

The invention relates to an electrochromic device having  
     (a) a pair of glass or plastic plates or plastic films wherein at least one such plate or film is provided on one side each with an electrically conductive coating, wherein  
     (1) at least one such plate or film and its conductive coating ist transparent,  
     (2) the other such plate or film and its conductive coating is optionally mirrored,  
     (3) the electrically conductive layer of one or both of the two plates or films is optionally divided into separate segments optionally provided with individual contacts, and  
     (4) the plates or films are joined on the sides of their conductive coating by means of a sealing ring to form a volume; and  
     (b) the volume formed by the two plates or films and the sealing ring is filled with an electrochromic medium containing certain dihydronaphthazines or dihydrophenazines.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an electrochromic device havingimproved light stability.

[0002] Electrochromic devices are already known, for example from D.Theis in Ullmann's Encyclopaedia of Industrial Chemistry, Vol. A 8, page622 (Verlag Chemie, 1987), and WO-A 94/23333. A distinction is madebetween two basic types:

[0003] Type 1: full-area electrochromic devices;

[0004] Type 2: electrochromic display devices having structuredelectrodes.

[0005] Type I is used, for example, in electrically darkenable windowpanes or electrically dimmable automobile mirrors. Such devices aredisclosed, for example, in U.S. Pat. No. 4,902,108.

[0006] Type 2 is used in segment and matrix displays. Such displaydevices are proposed, for example, in DE-A 196 31 728. Devices of thistype can be observed transmissively or, in the case of reflection,reflectively.

[0007] WO-A 94/23333 compares electrochromic materials having differentconstructions, but these are not used as display devices:

[0008] Construction a: the electrochromic substances are in the form ofa fixed film or layer on the electrodes (see Ullmann, above).

[0009] Construction b: the electrochromic substances are deposited onthe electrodes as a layer by the redox process (see Ullmann, above).

[0010] Construction c: the electrochromic substances remain permanentlyin solution.

[0011] For construction (a), the best-known electrochromic material isthe tungsten oxide/palladium hydride pair.

[0012] For construction (b), viologens have been described aselectrochromic substances. These devices are not self-erasing, i.e., theimage produced remains after the current has been switched off and canbe erased again only by reversing the voltage. Such devices are notparticularly stable and do not allow a large number of switching cycles.

[0013] In addition, the cells constructed using tungsten oxide/palladiumhydride in particular cannot be operated in transmitted light, but onlyreflectively, owing to light scattering at these electrochromic layers.

[0014] Elektrokhimiya, 13, 32-37 (1977), 13, 404-408, 14, 319-322(1978), U.S. Pat. No. 4,902,108, and U.S. Pat. No. 5,140,455 disclose anelectrochromic system of construction (c). An electrochromic cell builtup from glass plates with a conductive coating contains a solution of apair of electrochromic substances in an inert solvent.

[0015] The pair of electrochromic substances used is oneelectrochemically reversibly reducible substance and one reversiblyoxidizable substance. Both substances are colorless or only weaklycolored in the ground state. Under the action of an electric voltage,one substance is reduced and the other oxidized, both becoming colored.When the voltage is switched off, the ground state re-forms in the caseof both substances, decolorization or a color lightening taking place.

[0016] U.S. Pat. No. 4,902,108 discloses that suitable pairs of redoxsubstances are those in which the reducible substance has at least twochemically reversible reduction waves in the cyclic voltammogram and theoxidizable substance correspondingly has at least two chemicallyreversible oxidation waves.

[0017] According to WO-A 94/23333, however, such solution systems ofconstruction (c) have serious disadvantages. Diffusion of theelectrochromic substances in the solution causes fuzzy color boundariesand high power consumption in order to maintain the colored state, sincethe colored substances are permanently degraded by recombination andreaction at the opposite electrode in each case. Nevertheless, variousapplications have been described for such electrochromic cells ofconstruction (c). For example, they can be formed as automobilerear-view mirrors which can be darkened during night driving byapplication of a voltage and thus prevent dazzling by the headlamps offollowing vehicles. See U.S. Pat. Nos. 3,280,701, 4,902,108, and EP-A 0435 689. Furthermore, such cells can also be employed in window panes orautomobile sunroofs, where they darken the sunlight after application ofa voltage. Likewise described is the use of such devices aselectrochromic display devices, for example in segment or matrixdisplays having structured electrodes. See DE-A 196 31 728.

[0018] The electrochromic cells normally consist of a pair of glassplates, of which, in the case of the automobile mirror, one is mirrored.One side of these sheets is full-area coated with a light-transparent,electroconductive layer, for example, indium-tin oxide (ITO), where, inthe case of display devices, this conductive coating is divided intoelectrically separated segments provided with individual contacts. Thesesheets are used to construct a cell by bonding them by means of asealing ring with their electroconductively coated sides facing oneanother to form a cell. This cell is filled with an electrochromicliquid through an opening and the cell is tightly sealed. The two sheetsare connected to a voltage source via the ITO layers.

[0019] The electrochromic devices described above generally exhibitsensitivity to light, in particular UV light. Electrochromic devicescontaining UV absorbers have therefore been described, for example, inU.S. Pat. No. 5,280,380.

[0020] Compared with the use of UV absorbers, the use of electrochromiccompounds which inherently have better light stability would beadvantageous.

[0021] Surprisingly, it has now been found that the use of certaindihydronaphthazines or dihydrophenazines results in improved lightstability of the electrochromic device.

SUMMARY OF THE INVENTION

[0022] The invention accordingly relates to an electrochromic devicecomprising

[0023] (a) a pair of glass or plastic plates or plastic films wherein atleast one such plate or film (preferably both plates or films) isprovided on one side each with an electrically conductive coating,wherein

[0024] (1) at least one such plate or film and its conductive coatingist transparent,

[0025] (2) the other such plate or film and its conductive coating isoptionally mirrored,

[0026] (3) the electrically conductive layer of one or both of the twoplates or films is optionally divided into separate segments optionallyprovided with individual contacts, and

[0027] (4) the plates or films are joined on the sides of theirconductive coating by means of a sealing ring to form a volume; and

[0028] (b) the volume formed by the two plates or films and the sealingring is filled with an electrochromic medium comprising a pair ofelectrochromic substances OX₂ and RED₁, wherein

[0029] (1) OX₂ is a reducible electrochromic substance, and

[0030] (2) RED, is an oxidizable electrochromic substance represented byat least one of the formulas

[0031] wherein

[0032] R²⁰¹ is aryl,

[0033] R²⁰² is alkyl, cycloalkyl, alkenyl, aralkyl, or aryl,

[0034] B is a bivalent bridge,

[0035] m and n, independently of one another, are integers from 1 to 4,and

[0036] R²⁰³ to R²⁰⁶, independently of one another, are hydrogen,halogen, alkyl, alkoxy, cyano or aryl,

[0037] with the provisos that when m is at least 2, two adjacent R²⁰³together also optionally represent a bivalent —CH═CH—CH═CH— radical andwhen n is at least 2, two adjacent R²⁰⁴ together also optionallyrepresent a bivalent —CH═CH—CH═CH— radical.

BRIEF DESCRIPTION OF THE DRAWING

[0038]FIG. 1 shows a cell constructed according to Example 1 of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0039] Such dihydrophenazines are disclosed, for example, by H. Gilmanand J. J. Dietrich in J. Amer. Chem. Soc., 79, 6178 (1957) or can beprepared analogously.

[0040] Preferred dihydronaphthazines and dihydrophenazines of theformulas (CC) to (CCIII) are those in which

[0041] R²⁰¹ is C₆-C₁₀-aryl,

[0042] R²⁰² is C₁-C₁₂-alkyl, C₃-C₇-cycloalkyl, C₂-C₁₂-alkenyl,C₇-C₁₆-aralkyl, or C₆-C₀-aryl,

[0043] B is —(CH₂)_(p)—, —(CH₂)—(O—CH₂)_(q)—O—CH₂— or—(CH₂)_(r)—C₆H₄—(CH₂)_(s)—, where the CH₂ groups are optionallysubstituted by methyl,

[0044] R²⁰³ to R²⁰⁶, independently of one another, are hydrogen,halogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, cyano, or C₆-C₁₀-aryl,

[0045] m and n, independently of one another, are integers from 1 to 4,

[0046] with the provisos that when m is at least 2, two adjacent R²⁰³together can also represent a bivalent —CH═CH—CH═CH— radical and when nis at least 2, two adjacent R²⁰⁴ together can also represent a bivalent—CH═CH—CH═CH— radical,

[0047] p is an integer from 2 to 20, and

[0048] q, r, and s, independently of one another, are integers from 0 to10.

[0049] Particularly preferred dihydronaphthazines and dihydrophenazinesof the formulas (CC) to (CCIII) are those in which

[0050] R²⁰¹ is phenyl (which can optionally carry up to three methyl,methoxy, chlorine, bromine, or cyano radicals),

[0051] R²⁰² is optionally branched C₁-C₈-alkyl, cyclopentyl, cyclohexyl,benzyl, phenethyl, phenylpropyl, or phenyl (where these radicals canoptionally carry up to three methyl, methoxy, chlorine, bromine, orcyano radicals),

[0052] B is —(CH₂)_(p)—,

[0053] R²⁰³ to R²⁰⁶, independently of one another, are hydrogen,chlorine, bromine, methyl, ethyl, propyl, butyl, methoxy, ethoxy, cyano,or phenyl,

[0054] m and n, independently of one another, are integers from 1 to 2,

[0055] with the provisos that when m is at least 2, two adjacent R²⁰³together can also represent a bivalent —CH═CH—CH═CH— radical and when nis at least 2, two adjacent R²⁰⁴ together can also represent a bivalent—CH═CH—CH═CH— radical, and

[0056] p is an integer from 2 to 10.

[0057] In very particularly preferred form, the electrochromic deviceaccording to the invention comprises an RED, of the formula (CC).Preference is given to dihydrophenazines of the formula (CC) in which

[0058] R²⁰¹ is phenyl,

[0059] R²⁰² is methyl, ethyl, propyl, butyl, phenylpropyl, or phenyl(particularly preferably phenyl),

[0060] R²⁰³ and R²⁰⁴ are hydrogen, and

[0061] m and n are 1.

[0062] In a similarly preferred manner, the electrochromic deviceaccording to the invention comprises an RED, of the formula (CCII).Preference is given to dihydrophenazines of the formula (CCII) in which

[0063] R²⁰² is phenyl,

[0064] B is —(CH₂)_(p)—,

[0065] R²⁰³ and R²⁰⁴ are hydrogen,

[0066] m and n are 1, and

[0067] p is an integer from 2 to 6.

[0068] Besides electrochromic substances RED, of the formulas (CC) to(CCIII), the electrochromic device according to the invention comprisesat least one electrochromic substance OX₂. However, it can also comprisefurther RED₁ and/or OX₂ substances.

[0069] Through selection of the electrochromic compounds RED₁ and OX₂and/or mixtures thereof, any desired monochromic hues can beestablished. For a polychromic color display, two or more suchelectrochromic devices can be placed flat one on top of the other, witheach of these devices being capable of producing a different hue. Such astack is preferably built up in such a way that the devices in contactwith one another have a common light-transparent plate, which is thenprovided with a conductive coating on both sides and, depending on thedesign, divided into segments. A stack then consists, for example, ofthree electrochromic devices consisting of at least four plates. Byswitching on segments in various of these stacked devices, multicoloreddisplays can be achieved. If consecutive segments in different devicesof this kind are switched on, mixed colors are obtained. Thus, anydesired colors can be displayed in the context of trichromicity, i.e.,for example, colored images.

[0070] Preference is given to electrochromic devices according to theinvention which comprise an oxidizable substance RED, of the formulas(CC) to (CCIII) and a reducible substance OX₂ and, if desired, furtheroxidizable and/or reducible substances, where

[0071] (a) the reducible substance has at least one (preferably at leasttwo) chemically reversible reduction waves in the cyclic voltammogramand the oxidizable substance correspondingly has at least one(preferably at least two) chemically reversible oxidation waves, or

[0072] (b) the reducible substance and the oxidizable substance arecovalently bonded to one another via a bridge B, or

[0073] (c) the reducible and/or oxidizable substances selected are thosein which the reversible transition between the oxidizable form and thereducible form or vice versa is associated with the breaking or formingof a σ bond, or

[0074] (d) the reducible substance and/or the oxidizable substance aremetal salts or metal complexes of metals which exist in at least twooxidation states, or

[0075] (e) the reducible and/or oxidizable substances are oligomers andpolymers containing at least one of said redox systems, but also pairsof such redox systems as defined under (a) to (d), or

[0076] the reducible and/or oxidizable substance employed is a mixtureof the substances described in (a) to (e).

[0077] Suitable OX₂ and further RED₁ for the purposes of the inventionare substances which, on reduction or oxidation at the cathode or anodein the solvent mentioned, give products RED₂ and OX₁ which do notundergo any subsequent chemical reaction, but instead can be fullyoxidized or reduced back to OX₂ and RED₁.

[0078] Suitable reducible substances OX₂ are, for example:

[0079] in which

[0080] R² to R⁵, R⁸, R⁹, R¹⁶ to R¹⁹, independently of one another, areC₁-C₁₈-alkyl, C₂-C₁₂-alkenyl, C₄-C₇-cycloalkyl, C₇-C₁₅-aralkyl, orC₆-C₁₀-aryl, or

[0081] R⁴; R⁵ or R⁸; R⁹ together can form a —(CH₂)₂— or —(CH₂)₃— bridge,

[0082] R⁶, R⁷ and R²² to R²⁵, independently of one another, arehydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, halogen, cyano, nitro, orC₁-C₄-alkoxycarbonyl, or

[0083] R²²; R²³ and/or R²⁴; R²⁵ can form a —CH═CH—CH═CH— bridge,

[0084] R¹⁰; R¹¹, R¹⁰; R¹³, R¹²; R¹³ and R¹⁴; R¹⁵ independently of oneanother, are hydrogen or in pairs are a —(CH₂)₂—, —(CH₂)₃—, or —CH═CH—bridge,

[0085] R²⁰ and R²¹, independently of one another, are O, N—CN, C(CN)₂,or N—C₆ C₁₀-aryl,

[0086] R²⁶ and R²⁷ are hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, halogen,cyano, nitro, C₁-C₄-alkoxycarbonyl, or C₆-C₁₀-aryl,

[0087] R⁶⁹ to R⁷⁴, R⁸⁰ and R⁸¹, independently of one another, arehydrogen or C₁-C₆-alkyl, or

[0088] R⁶⁹; R¹² , R¹³, R⁷³ R⁸⁰ and/or R⁷⁴; R⁸¹ together form a—CH═CH—CH—CH— bridge,

[0089] E¹ and E², independently of one another, are O, S, NR¹, orC(CH₃)₂, or

[0090] E¹ and E² together form an —N—(CH₂)₂-N— bridge,

[0091] R¹ is C₁-C₁₈-alkyl, C₂-C₁₂-alkenyl, C₄-C₇-cycloalkyl,C₇-C₁₅-aralkyl, or C₆-C₁₀-aryl,

[0092] Z¹ is a direct bond or —CH═CH—, —C(CH₃)═CH—, —C(CN)═CH—,—CCl═CCl—, —C(OH)═CH—, —CCl═CH—, —C—C—, —CH═N—N═CH—,—C(CH₃)═N—N═C(CH₃)—, or —CCI—N—N═CCI—,

[0093] Z² is —(CH₂)_(r)— or —CH₂-C₆H₄—CH₂—,

[0094] r is an integer from 1 to 10,

[0095] R⁹⁴ and R⁹⁵, independently of one another, are hydrogen or cyano,

[0096] R¹⁰¹ to R¹⁰⁵, independently of one another, are C₆-C₁₀-aryl or anoptionally benzo-fused aromatic or quasi-aromatic, five- or six-memberedheterocyclic ring,

[0097] R¹⁰⁷, R¹⁰⁹, R¹¹³ and R¹¹⁴, independently of one another, are aradical of the formulas (CV) to (CVII)

[0098] R¹⁰⁸, R¹¹⁵ and R¹¹⁶, independently of one another, areC₆-C₁₀-aryl or a radical of the formula (CV),

[0099] R¹¹⁰ to R¹¹², R¹¹⁷ and R¹¹⁸, independently of one another, arehydrogen, C₁- to C₄-alkyl, halogen, or cyano,

[0100] E¹⁰¹ and E¹⁰², independently of one another, are O, S, or N—R¹¹⁹,

[0101] R¹¹⁹ and R¹²², independently of one another, are C₁-C₁₈-alkyl,C₂-C₈-alkenyl, C₄-C₇-cycloalkyl, C₇-C₁₅-aralkyl, or C₆-C₁₀-aryl,

[0102] R¹⁰⁶, R¹²⁰, R¹²¹, R¹²³ and R¹²⁴, independently of one another,are hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, halogen, cyano, nitro, orC₁-C₄-alkoxycarbonyl, or

[0103] R¹²⁰, R¹² or R¹²³, R¹²⁴ together form a —CH═CH—CH═CH— bridge,

[0104] A¹, A² and A³, independently of one another, are 0 or C(CN)₂,

[0105] R⁹⁶ is hydrogen, phenyl, or tert-butyl, and

[0106] X⁻ is an anion which is redox-inert under the conditions.

[0107] Examples of suitable oxidizable substances RED, are thefollowing:

[0108] in which

[0109] R²⁸ to R³¹, R³⁴, R³⁵, R³⁸, R³⁹, R⁴⁶, R⁵³ and R⁵⁴, independentlyof one another, are C₁-C₁₈-alkyl, C₂-C₁₂-alkenyl, C₄-C₇-cycloalkyl,C₇-C₁₅-aralkyl, or C₆-C₁₀-aryl,

[0110] R³², R³³, R³⁶, R³⁷, R⁴⁰, R⁴¹, R⁴² to R⁴⁵, R⁴⁷, R⁴⁸, R⁴⁹ to R⁵²and R⁵⁵ to R⁵⁸, independently of one another, are hydrogen, C₁-C₄-alkyl,C₁-C₄-alkoxy, halogen, cyano, nitro, C₁-C₄-alkoxycarbonyl, orC₆-C₁₀-aryl, and

[0111] R⁵⁷ and R⁵⁸ are additionally an aromatic or quasi-aromatic, five-or six-membered heterocyclic ring which is optionally benzo-fused, andR⁴⁸ is additionally NR⁷⁵R⁷⁶, or

[0112] R⁴⁹; R⁵⁰ and/or R⁵¹; R⁵² form a —(CH₂)₃—, —(CH₂)₄—, —(CH₂)₅—, or—CH═CH—CH═CH— bridge,

[0113] Z³ is a direct bond, a —CH═CH—, or —N═N— bridge,

[0114] ═Z⁴═ is a direct double bond, a ═CH—CH═, or ═N—N═ bridge,

[0115] E³ to E⁵, E¹⁰ and E¹¹, independently of one another, are O, S,NR⁵⁹, or C(CH₃)₂, and

[0116] E⁵ is additionally C═O or SO₂,

[0117] E³ and E⁴, independently of one another, can additionally be—CH═CH—,

[0118] E⁶ to E⁹, independently of one another, are S, Se, or NR⁵⁹,

[0119] R⁵⁹, R⁷⁵ and R⁷⁶, independently of one another, are C₁-C₁₂-alkyl,C₂-C₈-alkenyl, C₄-C₇-cycloalkyl, C₇-C₁₅-aralkyl, or C₆-C₁₀-aryl, and

[0120] R⁷⁵ is additionally hydrogen or R⁷⁵ and R⁷⁶ in the definition ofNR⁷⁵R⁷⁶ are, together with the N atom to which they are bonded, a five-or six-membered ring, which optionally contains further heteroatoms,

[0121] R⁶¹ to R⁶⁸, independently of one another, are hydrogen,C₁-C₆-alkyl, C₁-C₄-alkoxy, cyano, C₁-C₄-alkoxycarbonyl, or C₆-C₁₀-aryl,and

[0122] R⁶¹; R⁶² and R⁶⁷; R⁶⁸, independently of one another, additionallyform a —(CH₂)₃—, —(CH₂)₄—, or —CH═CH—CH═CH— bridge, or

[0123] R⁶²; R⁶³, R⁶⁴; R⁶⁵ and R⁶⁶; R⁶⁷ form a —O—CH₂CH₂—O— or—O—CH₂CH₂CH₂—O— bridge,

[0124] v is an integer between 0 and 100,

[0125] R⁸², R⁸³, R⁸⁸ and R⁸⁹, independently of one another, areC₁-C₁₈-alkyl, C₂-C₁₂-alkenyl, C₄-C₇-cycloalkyl, C₇-C₁₅-aralkyl, orC₆-C₁₀-aryl,

[0126] R⁸⁴ to R⁸⁷ and R⁹⁰ to R⁹³, independently of one another, arehydrogen or C₁-C₆-alkyl, or

[0127] R⁸⁴; R⁸⁶, R⁸⁵; R⁸⁷, R⁹⁰; R⁹² and/or R⁹¹; R⁹³ together form a—CH═CH—CH═CH— bridge.

[0128] Also suitable as RED₁ are anions, such as, for example, I⁻, I₃ ⁻,Br⁻, and SCN⁻.

[0129] Examples of optionally oligomeric or polymeric redox systemslinked via a bridge B are those of the formula

Y—[—(—B—Z—)_(a)—(—B—Y—)_(b)—]_(c)—B—Z  (L),

[0130] in which

[0131] Y and Z, independently of one another, are an OX₂ or RED₁radical, where either at least one Y is OX₂ and at least one Z is RED₁or Y and Z are OX₂,

[0132] where

[0133] OX₂ is the radical of a reversibly electrochemically reducibleredox system, and

[0134] RED₁ is the radical of a reversibly electrochemically oxidizableredox system,

[0135] B is a bridging unit,

[0136] c is an integer from 0 to 1000, and

[0137] a and b, independently of one another, are integers from 0 to100.

[0138] (a+b)−c is preferably ≦10,000.

[0139] The term reversibly electrochemically reducible or oxidizablehere is taken to mean that electron transfer can take place with orwithout a change in the a structure entirely within the sense of theabove-mentioned definition of OX₂ and RED₁ according to the invention.

[0140] The electrochromic compounds of the formula (L) are in particulartaken to mean those of the formulas

OX₂—B—RED₁  (La),

OX₂—B—RED₁—B—OX₂  (Lb),

RED₁—B—OX₂—B—RED₁  (Lc),

OX₂—(B—RED₁—B—OX₂)_(d)—B—RED₁  (Ld)

[0141] or

OX₂—(B—OX₂)_(e)—B—OX₂  (Le)

[0142] in which

[0143] OX₂, RED, and B are as defined above,

[0144] d is an integer from 1 to 5, and

[0145] e is an integer from 0 to 5.

[0146] OX₂ and RED₁ in the formulas (L) and (La) to (Le) are taken tomean, in particular, radicals of the above-described redox systems ofthe formulas (I) to (X), (CI) to (CIV), and (XX) to (XXXIII) in whichthe bonding to the bridging unit B takes place via one of the radicalsR² to R¹⁹, R²² to R²⁷, R²⁸ to R⁵⁸, R⁶¹, R⁶², R⁶⁷, R⁶⁸, R⁶³, R⁸⁸, or R¹²²or, where one of the radicals E¹ or E² is NR¹ or one of the radicals E³to E¹¹ is NR⁵⁹ or one of the radicals E¹⁰¹ to E¹⁰² is NR¹¹⁹, takes placevia R¹, R⁵⁹, or R¹¹⁹, and said radicals are then a direct bond, and

[0147] B is a bridge of the formula —(CH₂)_(n)— or —[Y¹_(s)(CH₂)_(m)—Y²]_(o)—(CH₂)_(p)—Y³ ^(q)—, which may be substituted byC₁-C₄-alkyl, C₁-C₄-alkoxy, halogen, or phenyl,

[0148] Y¹ to Y³, independently of one another, are O, S, NR⁶⁰, COO,CONH, NHCONH, cyclopentanediyl, cyclohexanediyl, phenylene, ornaphthylene,

[0149] R⁶⁰ is C₁-C₆-alkyl, C₂-C₆-alkenyl, C₄-C₇-cycloalkyl,C₇-C₁₅-aralkyl, or C₆-C₁₀-aryl,

[0150] n is an integer from 1 to 12,

[0151] m and p, independently of one another, are integers from 0 to 8,

[0152] o is an integer from 0 to 6, and

[0153] q and s, independently of one another, are 0 or 1.

[0154] OX₂ and RED₁ in the formulas (L) and (La) to (Le) are veryparticularly taken to mean radicals of the above-described redox systemsof the formulas (I), (V), (XX), (XXII), (XXIII), (XXV), (XXVI), and(XXXIII).

[0155] In another type of oligomeric or polymeric system, the OX₂ and/orRED₁ groups can also be bonded with a main group, for example, as sidechains, for example, to a poly(meth)acrylate, silicone, polycarbonate,polyurethane, polyurea, polyester, polyamide, cellulose, or otheroligomeric or polymeric systems.

[0156] Examples of metal salts or metal complexes which can be employedas OX₂ or RED₁ are Fe^(3+/2+), Ni^(3+/2+), Co^(3+/2+), Cu^(2+/+),[Fe(CN)₆]^(3−/4−), Fe₄[Fe(CN)₆]₃ ^(0/4−), [Co(CN)₆]^(3−/) ⁴⁻,[Fe(cyclopentadienyl)₂]^(0/+), Lu(Pc)^(2+ to 2−) (where Pc isphthalocyanine), and Fe[Fe(CN)₆]^(0/1−).

[0157] Suitable counterions for metal ions and cationic complexes areall redox-inert anions X⁻, as described more precisely later, andsuitable counterions of the anionic complexes are all redox-inertcations M′⁺, for example, alkali metals or quaternary ammonium salts,such as Na⁺, K⁺, N(CH₃)₄ ⁺, N(C₄H₉)₄ ⁺, and C₆H₅CH₂N(CH₃)₃ ⁺, andothers.

[0158] Preference is likewise given to an electrochromic devicecontaining mixtures of the electrochromic substances mentioned above ingeneral and preferred terms. Examples of such mixtures are(I)+(CI)+(CC), (I)+(IV)+(CC)+(XXII), (La)+(I)+(CC)+(XXVI), without thisbeing intended to express any restriction.

[0159] The mixing ratios are variable within broad limits. They allow adesired hue or degree of blackness to be optimized and/or the desireddynamics of the device to be optimized.

[0160] In the substituent definitions given above, alkyl radicals,including derivatives, are, for example, alkoxy or aralkyl radicals,preferably those having 1 to 12 C atoms, in particular having 1 to 8 Catoms, unless stated otherwise. They can be straight-chain or branchedand can optionally carry further substituents, such as C₁-C₄-alkoxy,fluorine, chlorine, hydroxyl, cyano, C₁-C₄-alkoxycarbonyl, or COOH. Theterm cycloalkyl radicals is preferably taken to mean those having 3 to 7carbon atoms, in particular having 5 or 6 carbon atoms. Alkenyl radicalsare preferably those having from 2 to 8 carbon atoms, in particular 2 to4 carbon atoms.

[0161] Aryl radicals, including those in aralkyl radicals, are phenyl ornaphthyl radicals, in particular phenyl radicals. They can besubstituted by 1 to 3 of the following radicals: C₁-C₆-alkyl,C₁-C₆-alkoxy, fluorine, chlorine, bromine, cyano, hydroxyl,C₁-C₆-alkoxycarbonyl, or nitro. Two adjacent radicals can also form aring.

[0162] The term optionally benzo-fused aromatic or quasi-aromatic, five-or six-membered heterocyclic rings is taken to mean, in particular,imidazole, benzimidazole, oxazole, benzoxazole, thiazole, benzothiazole,indole, pyrazole, triazole, thiophene, isothiazole, benzisothiazole,1,3,4- or 1,2,4-thiadiazole, pyridine, quinoline, pyrimidine, andpyrazine. They may be substituted by 1 to 3 of the following radicals:C₁-C₆-alkyl, C₁-C₆-alkoxy, fluorine, chlorine, bromine, cyano, nitro,hydroxyl, mono- or di-C₁-C₆-alkylamino, C₁-C₆-alkoxycarbonyl,C₁-C₆-alkylsulfonyl, C₁-C₆-alkanoylamino, phenyl, or naphthyl. Twoadjacent radicals may also form a ring.

[0163] The electrochromic substances are either known (e.g., Topics inCurrent Chemistry, Vol. 92, pages 1-44, (1980), Angew. Chem., 90, 927(1978), Adv. Mater., 3, 225, (1991), German Offenlegungsschrift3,917,323, J. Am. Chem. Soc., 117, 8528 (1995), J. C. S., Perkin II,1990, 1777, German Offenlegungsschrift 4,435,211, EP-A 476,456, EP-A476,457, German Offenlegungsschrift 4,007,058, J. Org. Chem., 57, 1849(1992), and J. Am. Chem. Soc., 99, 6120, 6122 (1977)) or can be preparedanalogously. The compounds of the formula (L) are likewise known. E.g.,WO 97/30134.

[0164] Synthetically required ions, such as bromide, are subsequentlyreplaced by redox-inert ions.

[0165] Besides the oxidizable compounds of the formula (CC) or (CCII)according to the invention, particular preference is given to thereducible electrochromic compounds of the formulas (I), (II), (III),(IV), and (V).

[0166] Besides the oxidizable compounds of the formula (CC) or (CCII)according to the invention, very particular preference is given to thereducible electrochromic compounds of the formulas (I), (IV) and (V)

[0167] in which

[0168] R₂, R³ and R⁹ , independently of one another, are methyl, ethyl,propyl, butyl, pentyl, hexyl, heptyl, benzyl, phenethyl, phenylpropyl,phenyl, 2-methylphenyl, or 2,6-dimethylphenyl or

[0169] R⁸ and R⁹ together form a —(CH₂)₂— or —(CH₂)₃— bridge,

[0170] R¹⁰ to R¹⁵ are hydrogen,

[0171] R⁶⁹ to R⁷³, R⁸⁰ and R⁸¹, independently of one another, arehydrogen or methyl, or

[0172] R¹²; R⁶⁹, R¹³; R⁷⁰, R⁷³; R⁸⁰ and/or R⁷⁴; R⁸¹ form a —CH═CH—CH═CH—bridge,

[0173] Z¹ is a direct bond or —CH═CH—, and

[0174] X⁻ is an anion which is redox-inert under the conditions,

[0175] where the alkyl radicals may be branched, for example 2-butyl and1-phenyl-2-propyl.

[0176] Very outstandingly suitable for the purposes of the invention arethe electrochromic compounds of the formula (I) in which

[0177] R² and R³ are identical and are methyl, ethyl, butyl, heptyl, orphenylpropyl,

[0178] R¹² to R¹⁵ and R⁶⁹ to R⁷² are hydrogen,

[0179] Z¹ is a direct bond, and

[0180] X⁻ is a redox-inert anion or I⁻.

[0181] The light-protected electrochromic device according to theinvention preferably contains, in its electrochromic medium, at leastone solvent in which the electrochromic substances, if used with aconductive salt and if used with further additives, are dissolved. Thesolvent can also have been thickened in the form of a gel, for exampleby polyelectrolytes, porous solids or nanoparticles having large activesurface areas.

[0182] Suitable solvents are all solvents which are redox-inert underthe selected voltages and which cannot eliminate electrophiles ornucleophiles or themselves react as sufficiently strong electrophiles ornucleophiles and thus could react with the colored free-radical ions.Examples are propylene carbonate, γ-butyrolactone, acetonitrile,propionitrile, benzonitrile, glutaronitrile, methylglutaronitrile,3,3′-oxydipropionitrile, hydroxypropionitrile, dimethylformamide,N-methylpyrrolidone, sulfolane, 3-methylsulfolane, or mixtures thereof.Preference is given to propylene carbonate, benzonitrile, and mixtureswith one another or with glutaronitrile or 3-methylsulfolane. Particularpreference is given to propylene carbonate. Particular preference islikewise given to benzonitrile.

[0183] The electrochromic solution can contain at least one inertconductive salt. In particular if at least one of the substances of theredox pair RED₁/OX₂ is of an ionic nature, the addition of a conductivesalt, can be omitted.

[0184] Suitable inert conductive salts are lithium, sodium andtetraalkylammonium salts, in particular the latter. The alkyl groups cancontain between 1 and 18 carbon atoms and can be identical or different.Preference is given to tetrabutylammonium. Suitable anions for thesesalts, in particular as anions X⁻ in the formulas (I) to (VI), (CI),(CII) and (CV) to (CVII) and in the metal salts, are all redox-inert,colorless anions.

[0185] Examples are tetrafluoroborate, tetraphenylborate,cyanotriphenylborate, tetramethoxyborate, tetrapropoxyborate,tetraphenoxyborate, perchlorate, chloride, nitrate, sulfate, phosphate,methanesulfonate, ethanesulfonate, tetradecanesulfonate,pentadecanesulfonate, trifluoromethanesulfonate,perfluorobutanesulfonate, perfluorooctanesulfonate, benzenesulfonate,chlorobenzenesulfonate, toluenesulfonate, butylbenzenesulfonate,tert-butylbenzenesulfonate, dodecylbenzenesulfonate,trifluoromethylbenzenesulfonate, hexafluorophosphate,hexafluoroarsenate, hexafluorosilicate, or 7,8- or7,9-dicarbanido-undecaborate(-1) or (-2), which are optionallysubstituted on the B and/or C atoms by one or two methyl, ethyl, butylor phenyl groups, dodecahydrodicarbadodecaborate(-2) orB-methyl-C-phenyl-dodecahydrodicarbadodecaborate(-1).

[0186] Likewise suitable, including as anions X⁻ in the formulas (I) to(VI), (CI), (CII) and (CV) to (CVII) and in the metal salts, are theabove-mentioned anions which can also take on the role of an RED₁, forexample, I⁻ and I₃ ⁻.

[0187] The conductive salts are preferably employed in the range from 0to 1 mol/l.

[0188] Further additives which can be employed are thickeners in orderto control the viscosity of the electroactive solution. This can be ofimportance for avoiding segregation, i.e. the formation of coloredstreaks or spots on extended operation of the electrochromic device inthe switched-on state, and for controlling the fading rate after thecurrent is switched off.

[0189] Suitable thickeners are all compounds usual for this purpose,such as, for example, polyacrylate, polymethacrylate (Luctite L®),polycarbonate, or polyurethane.

[0190] Suitable further additives for the electrochromic solution forthe desired protection against UV light (<350 nm) from case to case areUV absorbers. Examples are UVINUL® 3000 (2,4-dihydroxybenzophenone,BASF), SANDUVOR® 3035 (2-hydroxy-4-n-octyloxybenzophenone, Clariant),Tinuvin® 571 (2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, Ciba),Cyasorb 24™ (2,2′-dihydroxy-4-methoxy-benzophenone, American CyanamidCompany), UVINUL® 3035 (ethyl 2-cyano-3,3-diphenylacrylate, BASF),UVINUL® 3039 (2-ethylhexyl 2-cyano-3,3-diphenyl-acrylate, BASF), UVINUL®3088 (2-ethylhexyl p-methoxycinnamate, BASF), and CHIMASSORB® 90(2-hydroxy-4-methoxy-benzophenone, Ciba). Preference is given to thefour last-mentioned compounds. Preference is likewise given to mixturesof UV absorbers, for example, of the four last-mentioned compounds.Particular preference is given to the mixture of UVINUL® 3039 andCHIMASSORB® 90.

[0191] The UV absorbers are employed in the range from 0.01 to 2 mol/l,preferably from 0.04 to 1 mol/l.

[0192] The electrochromic solution contains the electrochromicsubstances OX₂ and RED₁, in particular those of the formulas (1) to (X)and (CC) and/or (CCII), in each case in a concentration of at least 10⁻⁴mol/l (preferably from 0.001 to 0.5 mol/l). The total concentration ofall electrochromic substances present is preferably less than 1 mol/l.

[0193] In order to operate the electrochromic device according to theinvention, a constant, pulsed or amplitude-varying, for example,sinusoidal, direct current is used. The voltage depends on the desiredcolor depth, but in particular on the reduction or oxidation potentialsof the OX₂ and RED₁ used. Such potentials can be found, for example, inTopics in Current Chemistry, Volume 92, pp. 1-44, (1980) or Angew.Chem., 90, 927 (1978) or in the references cited therein. The differencein their potentials is a guide for the requisite voltage, but theelectrochromic device can be operated at lower or higher voltage. Inmany cases, for example on use of OX₂ of formula (I) or (V) and RED₁ offormula (CC), this potential difference necessary for operation is ≦1 V.Such electrochromic devices can therefore be supplied in a simple mannerwith the current from photovoltaic silicon cells.

[0194] If the voltage is switched off, the electrochromic deviceaccording to the invention returns to its original state. This erasingcan be considerably accelerated if the contacted segments or plates areshort-circuited. The display can also be erased very rapidly by repeatedreversal of the voltage, optionally also with simultaneous reduction inthe voltage.

[0195] By varying the layer thickness of the electrochromic device, theviscosity of the electrochromic solution and/or the diffusibility ordriftability of the electrochromic substances, the switch-on andswitch-off times of the display device can be modified within broadlimits. Thus, for example, thin layers exhibit shorter switching timesthan thick layers. It is thus possible to construct fast- andslow-switchable devices and thus to match them to the particularapplications in an optimum manner.

[0196] In slow devices, in particular display devices, a power-saving orrefresh mode can be used in the switched-on state in order to maintainthe displayed information. After the information to be displayed hasbeen built up, for example by direct voltage of sufficient level whichis constant or varying with high frequency or pulsed, the voltage isswitched to pulsed or varying direct voltage of low frequency, with thecontacting of the segments not being short-circuited during the phasesin which the voltage is zero. This low frequency can be, for example, inthe region of 1 Hz or lower, while the durations of the switch-on andswitch-off phases need not be of equal lengths, but instead, forexample, the switch-off phases can be significantly longer. Since thecolor depth of the displayed information drops only slowly during thecurrent pauses in the non-short-circuited state, relatively shortcurrent pulses are sufficient to compensate for these losses again inthe subsequent refresh phase. In this way, a flicker-free image withvirtually constant color depth is obtained, but its maintenance requiresonly a fraction of the current that would arise in the case of permanentcurrent flow.

[0197] Specific embodiments of the above-mentioned types 1 and 2 can be,for example, the following, which are likewise the subject-matter of theinvention if they comprise the electrochromic substances according tothe invention.

[0198] Type 1: (Non-mirrored)

[0199] From the light protection/light filter area: window panes forbuildings, road vehicles, aircraft, railways, ships, roof glazing,automobile sunroofs, glazing of greenhouses and conservatories, lightfilters of any desired type;

[0200] From the security/confidentiality area: separating panes for roomdividers in offices, road vehicles, aircraft, railways, sight protectionscreens, for example at bank counters, door glazing, visors formotorcycle or pilot helmets;

[0201] From the design area: glazing of ovens, microwave equipment,other domestic appliances, furniture;

[0202] From the display area: analogue voltage displays, as batterytesters, tank displays, and temperature displays.

[0203] Type 1: (Mirrored)

[0204] Mirrors of all types for road vehicles, railways, in particular,planar, spherical, aspherical mirrors, and combinations thereof, such asspherical/aspherical mirror glazing in furniture.

[0205] Type 2:

[0206] Display devices of all types, segment or matrix displays forwatches, computers, electrical equipment, electronic equipment, such asradios, amplifiers, TV sets, CD players, destination displays in busesand trains, departure displays in stations and airports, flat screens,and all applications mentioned under types 1 and 2 which contain atleast one switchable static or variable display device, such asseparating screens containing displays such as “Please do not disturb”,“Counter closed”, for example, automobile mirrors containing displays ofany desired type, such as display of the temperature, faults in thevehicle, for example, oil temperature, open doors, time, compassdirection.

[0207] The invention furthermore relates to dihydrophenazines of theformulas (CC) in which

[0208] R²⁰¹ is aryl (particularly C₆-C₁₀-aryl),

[0209] R²⁰² is C₂-C₁₂-alkyl, C₃-C₇-cycloalkyl, C₂-C₁₂-alkenyl, orC₇-C₁₆-aralkyl,

[0210] R²⁰³ and R²⁰⁴, independently of one another, are hydrogen,halogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, cyano, or C₆-C₁₀-aryl,

[0211] m and n, independently of one another, are integers from 1 to 4,or

[0212] two adjacent R²⁰³ and R²⁰⁴, independently of one another, are abivalent —CH═CH—CH═CH— radical if m or n is at least 2.

[0213] In particular in dihydrophenazines of the formulas (CC),

[0214] R²⁰¹ is phenyl, which can optionally carry up to three methyl,methoxy, chlorine, bromine, or cyano radicals,

[0215] R²⁰² is optionally branched C₂-C₈-alkyl, cyclopentyl, cyclohexyl,benzyl, phenethyl, or phenylpropyl,

[0216] R²⁰³ and R²⁰⁴, independently of one another, are hydrogen,chlorine, bromine, methyl, ethyl, propyl, butyl, methoxy, ethoxy, cyano,or phenyl,

[0217] m and n, independently of one another, are integers from 1 to 2,or

[0218] two adjacent R²⁰³ and R²⁰⁴, independently of one another, are abivalent —CH═CH—CH═CH— radical if m or n is 2.

[0219] Very particularly in dihydrophenazines of the formula (CC),

[0220] R²⁰¹ is phenyl,

[0221] R²⁰² is ethyl, propyl, butyl, phenylethyl, or phenylpropyl,

[0222] R²⁰³ and R²⁰⁴ are hydrogen, and

[0223] m and n are 1.

[0224] The invention furthermore relates to dihydrophenazines of theformula (CCII) in which

[0225] R²⁰² is alkyl, cycloalkyl, alkenyl, aralkyl, or aryl,particularly C₁-C₁₂-alkyl, C₃-C₇-cycloalkyl, C₂-C₁₂-alkenyl,C₇-C₁₆-aralkyl, or C₆-C₁₀-aryl,

[0226] B is a bivalent bridge, particularly —(CH₂)_(p)—,—(CH₂)—(O—CH₂)_(q)—O—CH₂— or —(CH₂)_(r)—C₆H₄—(CH₂)_(s)—, where the CH₂groups may be substituted by methyl,

[0227] R²⁰³ and R²⁰⁴, independently of one another, are hydrogen,halogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, cyano, or C₆-C₁₀-aryl,

[0228] m and n, independently of one another, are integers from 1 to 4,or

[0229] two adjacent R²⁰³ and R²⁰⁴, independently of one another, are abivalent —CH═CH—CH═CH— radical if m or n is at least 2,

[0230] p is an integer from 2 to 20, and

[0231] q, r, and s, independently of one another, are integers from 0 to10.

[0232] In particular in dihydrophenazines of the formula (CCII),

[0233] R²⁰² is optionally branched C₂-C₈-alkyl, cyclopentyl, cyclohexyl,benzyl, phenethyl, phenylpropyl, or phenyl, where these radicals canoptionally carry up to three methyl, methoxy, chlorine, bromine, orcyano radicals,

[0234] B is —(CH₂)_(p)—,

[0235] R²⁰³ and R²⁰⁴, independently of one another, are hydrogen,chlorine, bromine, methyl, ethyl, propyl, butyl, methoxy, ethoxy, cyano,or phenyl,

[0236] m and n, independently of one another, are integers from 1 to 2,or

[0237] two adjacent R²⁰³ and R²⁰⁴, independently of one another, are abivalent —CH═CH—CH═CH— radical if m or n is 2, and

[0238] p is an integer from 2 to 10.

[0239] Very particularly in dihydrophenazines of the formula (CCII),

[0240] R²⁰² is methyl, ethyl, propyl, butyl, phenethyl, phenylpropyl, orphenyl,

[0241] B is —(CH₂)_(p)—,

[0242] R²⁰³ and ²⁰⁴ are hydrogen,

[0243] m and n are 1, and

[0244] p is an integer from 3 to 5.

[0245] To a very particular extent in dihydrophenazines of the formula(CCII)

[0246] R²⁰² is phenyl,

[0247] B is —(CH₂)_(p)—,

[0248] R²⁰³ and R²⁰⁴ are hydrogen,

[0249] m and n are 1, and

[0250] p is 3 or 4.

[0251] The following examples further illustrate details forrepresentative embodiments of this invention. The invention, which isset forth in the foregoing disclosure, is not to be limited either inspirit or scope by these examples. Those skilled in the art will readilyunderstand that known variations of the conditions and processes of thefollowing preparative procedures can be used to prepare thesecompositions. Unless otherwise noted, all temperatures are degreesCelsius and all percentages are percentages by weight.

EXAMPLES Example 1

[0252] A cell was constructed as shown in FIG. 1. To this end, two glassplates 1 and 2 that were coated on one surface with ITO were used.

[0253] A mixture of 97% of photocuring DELO-Katiobonde 4594 epoxyadhesive (DELO Industrieklebstoffe, Landsberg) and 3% of glass beadshaving a diameter of 200 μm were applied in a ring shape (3, see FIG. 1)to the ITO-coated side of glass plate 1 in such a way that a 2 mm wideopening (4, see FIG. 1) was left. Glass plate 2 was then placed on theadhesive bead in such a way that the ITO layers of the two plates 1 and2 faced each other and a geometry as shown in FIG. 1 was formed. Theadhesive was cured by exposure for 10 minutes to daylight in thevicinity of a window and then for 20 minutes at 105° C. withoutexposure.

[0254] A dish was filled under a nitrogen atmosphere with a solutionwhich was 0.02 molar with respect to the electrochromic compounds of theformulas

[0255] and 0.1 molar with respect to each of the UV absorbers of theformulas

[0256] in anhydrous, oxygen-free propylene carbonate.

[0257] The cell was then placed vertically in the dish under a nitrogenatmosphere in such a way that the opening 4 was located beneath theliquid level. The dish with the cell was placed in a desiccator, whichwas evacuated to 0.05 mbar and then carefully aerated with nitrogen.During the aeration, the electrochromic solution rose through theopening 4 into the cell and, apart from a small bubble, filled theentire volume. The cell was removed from the solution, cleaned at theopening 4 under a nitrogen atmosphere by wiping with a paper towel, andsealed with the photochemically curable acrylate adhesiveDELO-Photobond® 4497 (DELO Industrieklebstoffe, Landsberg). The cell wasthen exposed for 1 minute under a nitrogen atmosphere with a DELOLUX® 03lamp (DELO Industrieklebstoffe, Landsberg) at a distance of 8 cm fromthe opening 4, and cured at room temperature overnight under a nitrogenatmosphere.

[0258] Application of a voltage of 0.9 V to the two plates 1 and 2caused the cell rapidly to turn a deep greenish blue. Switching off thevoltage and short-circuiting the contacts caused the color rapidly todisappear again.

[0259] The following electrochromic compounds of Examples 2 to 12 wereemployed entirely analogously: Ex. OX₂ 2

3

4

5

6

7

8

9

10 

11 

12 

Ex. RED₁ 2

3

4

5

6

7

8

9

10 

11 

12 

What is claimed is:
 1. An electrochromic device comprising (a) a pair ofglass or plastic plates or plastic films wherein at least one such plateor film is provided on one side each with an electrically conductivecoating, wherein (1) at least one such plate or film and its conductivecoating ist transparent, (2) the other such plate or film and itsconductive coating is optionally mirrored, (3) the electricallyconductive layer of one or both of the two plates or films is optionallydivided into separate segments optionally provided with individualcontacts, and (4) the plates or films are joined on the sides of theirconductive coating by means of a sealing ring to form a volume; and (b)the volume formed by the two plates or films and the sealing ring isfilled with an electrochromic medium comprising a pair of electrochromicsubstances OX₂ and RED₁, wherein (1) OX₂ is a reducible electrochromicsubstance, and (2) RED₁ is an oxidizable electrochromic substancerepresented by at least one of the formulas

wherein R²⁰¹ is aryl, R²⁰⁰ is alkyl, cycloalkyl, alkenyl, aralkyl, oraryl, B is a bivalent bridge, m and n, independently of one another, areintegers from 1 to 4, and R²⁰³ to R²⁰⁶, independently of one another,are hydrogen, halogen, alkyl, alkoxy, cyano or aryl, with the provisosthat when m is at least 2, two adjacent R²⁰³ together also optionallyrepresent a bivalent —CH═CH—CH═CH— radical and when n is at least 2, twoadjacent R²⁰⁴ together also optionally represent a bivalent—CH═CH—CH═CH— radical.
 2. An electrochromic device according to claim 1wherein RED, represents one of the formulas (CC), (CCI), (CCII), or(CCIII) wherein R²⁰¹ is C₆-C₁₀-aryl, R²⁰² is C₁-C₁₂-alkyl,C₃-C₇-cycloalkyl, C₂-C₁₂-alkenyl, C₇-C₁₆-aralkyl, or C₆-C₁₀-aryl, B is—(CH₂)_(p)—, —(CH₂)—(O—CH₂)_(q) O—CH₂— or —(CH₂)_(r)—C₆H₄—(CH₂)_(s)—,where the CH₂ groups may be substituted by methyl, R²⁰³ to R²⁰⁶,independently of one another, are hydrogen, halogen, C₁-C₄-alkyl,C₁-C,-alkoxy, cyano, or C₆-C₁₀-aryl, m and n, independently of oneanother, are integers from 1 to 4, with the provisos that when m is atleast 2, two adjacent R²⁰³ together also optionally represent a bivalent—CH═CH—CH═CH— radical and when n is at least 2, two adjacent R²⁰⁴together also optionally represent a bivalent —CH═CH—CH═CH— radical, pis an integer from 2 to 20, and q, r, and s, independently of oneanother, are integers from 0 to
 10. 3. An electrochromic deviceaccording to claim 1 wherein RED, represents one of the formulas (CC),(CCI), (CCII), or (CCIII) wherein R²⁰¹ is phenyl or phenyl carrying upto three methyl, methoxy, chlorine, bromine, or cyano radicals, R²⁰² isan optionally branched C₁-C₈-alkyl, cyclopentyl, cyclohexyl, benzyl,phenethyl, phenylpropyl radical wherein each such radical optionallycarries up to three methyl, methoxy, chlorine, bromine, or cyanoradicals, B is —(CH₂)_(p)—, R²⁰³ to R²⁰⁶, independently of one another,are hydrogen, chlorine, bromine, methyl, ethyl, propyl, butyl, methoxy,ethoxy, cyano, or phenyl, m and n, independently of one another, areintegers from 1 to 2, with the provisos that when m is at least 2, twoadjacent R²⁰³ together also optionally represent a bivalent—CH═CH—CH═CH— radical and when n is at least 2, two adjacent R²⁰⁴together also optionally represent a bivalent —CH═CH—CH═CH— radical, andp is an integer from 2 to
 10. 4. An electrochromic device according toclaim 1 wherein RED, represents the formula (CC) wherein R²⁰¹ is phenyl,R²⁰² is methyl, ethyl, propyl, butyl, phenylpropyl, or phenyl, R²⁰³ andR²⁰⁴ are hydrogen, and m and n are
 1. 5. An electrochromic deviceaccording to claim 4 wherein R²⁰¹ and R²⁰² are phenyl.
 6. Anelectrochromic device according to claim 1 wherein RED, represents theformula (CCII) wherein R²⁰² is phenyl, B is —(CH₂)_(p)—, R²⁰³ and R²⁰⁴are hydrogen, m and n are 1, and p is an integer from 2 to
 6. 7. Anelectrochromic device according to claim 6 wherein p is 3 to
 5. 8. Anelectrochromic device according to claim 1 wherein OX₂ comprises acompound selected from the formulas

wherein R² to R⁵, R⁸, R⁹, R¹⁶ to R¹⁹, independently of one another, areC₁-C₁₈-alkyl, C₂-C₁₂-alkenyl, C₄-C₇-cycloalkyl, C₇-C₁₅-aralkyl, orC₆-C₁₀-aryl, or R⁴; R⁵ or R⁸; R⁹ together can form a —(CH₂)₂— or —(CH₂)₃— bridge, R⁶, R⁷ and R²² to R²⁵, independently of one another, arehydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, halogen, cyano, nitro, orC₁-C₄-alkoxycarbonyl, or R²²; R²³ and/or R²⁴; R²⁵ can form a—CH═CH—CH═CH— bridge, R¹⁰; R¹¹, R¹⁰; R¹³, R¹²; R¹³ and R¹⁴; R¹⁵,independently of one another, are hydrogen or in pairs are a —(CH₂)₂—,—(CH₂)₃—, or —CH═CH— bridge, R²⁰ and R²¹, independently of one another,are O, N—CN, C(CN)₂, or N—C₆₋C₁₀-aryl, R²⁶ and R²⁷ are hydrogen,C₁-C₄-alkyl, C₁-C₄-alkoxy, halogen, cyano, nitro, C₁-C₄-alkoxycarbonyl,or C₆-C₁₀-aryl, R⁶⁹ to R⁷⁴, R⁸⁰ and R⁸¹, independently of one another,are hydrogen or C₁-C₆-alkyl, or R⁶⁹; R¹², R⁷⁰; R¹³, R⁷³, R⁸⁰ and/or R⁷⁴;R⁸¹ together form a —CH═CH—CH═CH— bridge, E¹ and E², independently ofone another, are O, S, NR¹, or C(CH₃)₂, or E¹ and E² together form an—N—(CH₂)₂-N— bridge, R¹ is C₁-C₁₈-alkyl, C₂-C₁₂-alkenyl,C₄-C₇-cycloalkyl, C₇-C₁₅-aralkyl, or C₆-C₁₀-aryl, Z¹ is a direct bond or—CH═CH—, —C(CH₃)═CH—, —C(CN)═CH—, —CCl═CCl—, —C(OH)═CH—, —CCl═CH—,—C≡C—, —CH═N—N═CH—, —C(CH₃)═N—N═C(CH₃)—, or —CCl—N—N═CCl—, Z² is—(CH₂)_(r)— or —CH₂—C₆H₄—CH₂—, r is an integer from 1 to 10, R⁹⁴ andR⁹⁵, independently of one another, are hydrogen or cyano, R¹⁰¹ to R¹⁰⁵,independently of one another, are C₆-C₁₀-aryl or an optionallybenzo-fused aromatic or quasi-aromatic, five- or six-memberedheterocyclic ring, R¹⁰⁷, R¹⁰⁹, R¹¹³ and R¹¹⁴, independently of oneanother, are a radical of the formulas (CV) to (CVII)

R¹⁰⁸, R¹¹⁵ and R¹¹⁶, independently of one another, are C₆-C₁₀-aryl or aradical of the formula (CV), R¹¹⁰ to R¹¹², R¹¹⁷ and R¹¹⁸, independentlyof one another, are hydrogen, C₁- to C₄-alkyl, halogen, or cyano, E¹⁰¹and E¹⁰², independently of one another, are 0, S, or N—R¹¹⁹, R¹¹⁹ andR¹²², independently of one another, are C₁-C₈-alkyl, C₂-C₈-alkenyl,C₄-C₇-cycloalkyl, C₇-C₁₅-aralkyl, or C₆-C₁₀-aryl, R¹⁰⁶, R¹²⁰, R¹²¹, R¹²³and R¹²⁴, independently of one another, are hydrogen, C₁-C₄-alkyl,C₁-C₄-alkoxy, halogen, cyano, nitro, or C₁-C₄-alkoxy-carbonyl, or R¹²⁰,R¹²¹ or R¹²³, R¹²⁴ together form a —CH═CH—CH═CH— bridge, A¹, A² and A³,independently of one another, are O or C(CN)₂, R⁹⁶ is hydrogen, phenyl,or tert-butyl, and X⁻ is an anion which is redox-inert under theconditions.
 9. A window, separating screen, sight protection screen,glazing, roof glazing, light filter, mirror, or display devicecomprising an electrochromic device according to claim
 1. 10. Adihydrophenazine of the formula (CC)

wherein R²⁰¹ is C₆-C₁₀-aryl, R²⁰² is C₁-C₁₂-alkyl, C₃-C₇-cycloalkyl,C₂-C₁₂-alkenyl, C₇-C₁₆-aralkyl, or C₆-C₁₀-aryl, R²⁰³ anci R²⁰⁴,independently of one another, are hydrogen, halogen, C₁-C₄-alkyl,C₁-C₄-alkoxy, cyano, or C₆-C₁₀-aryl, m and n, independently of oneanother, are integers from 1 to 4, with the provisos that when m is atleast 2, two adjacent R²⁰³ together also optionally represent a bivalent—CH═CH—CH═CH— radical and when n is at least 2, two adjacent R²⁰⁴together also optionally represent a bivalent —CH═CH—CH═CH— radical. 11.A dihydrophenazine of the formula (CCII)

wherein R²⁰² is C₁-C₁₂-alkyl, C₃-C₇-cycloalkyl, C₂-C₁₂-alkenyl,C₇-C₁₆-aralkyl, or C₆-C₁₀-aryl, B is —(CH₂)—, —(CH₂)—(O—CH₂)_(q)—O—CH₂—or —(CH₂)_(r)—C₆H₄—(CH₂)_(s)—, where the CH₂ groups are optionallysubstituted by methyl, R²⁰³ and R²⁰⁴, independently of one another, arehydrogen, halogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, cyano, or C₆-C₁₀-aryl, mand n, independently of one another, are integers from 1 to 4, with theprovisos that when m is at least 2, two adjacent R²⁰³ together alsooptionally represent a bivalent —CH═CH—CH═CH— radical and when n is atleast 2, two adjacent R²⁰⁴ together also optionally represent a bivalent—CH═CH—CH═CH— radical, p is an integer from 2 to 20, and q, r, and s,independently of one another, are integers from 0 to
 10. 12. Anelectrochromic medium comprising a pair of electrochromic substances OX₂and RED₁, wherein (1) OX₂ is a reducible electrochromic substance, and(2) RED₁ is an oxidizable electrochromic'substance represented by atleast one of the formulas

wherein R²⁰¹ is aryl, R²⁰² is alkyl, cycloalkyl, alkenyl, aralkyl, oraryl, B is a bivalent bridge, m and n, independently of one another, areintegers from 1 to 4, and R²⁰³ to R²⁰⁶, independently of one another,are hydrogen, halogen, alkyl, alkoxy, cyano or aryl, with the provisosat least 2, two adjacent R²⁰³ together also optionally represent abivalent —CH═CH—CH═CH— radical and when n is at least 2, two adjacentR²⁰⁴ together also optionally represent a bivalent —CH-═CH—CH═CH—radical.